1. Field of the Invention
This invention relates generally to transmissions interconnecting a rotary power source with a driven element under varying torque loads and more particularly to a stepless variable ratio transmission.
2. Related History
Automatic transmission drives heretofore adapted for commercial use in vehicular systems generally included a fluid coupling such as a torque converter which provided a controlled slip coupling between an engine or motive output shaft and a gear shift transmission unit. The transmission unit was adapted for shiftable configuration into a plurality of fixed gear ratios. Shifting, engagement and selection of gear ratios were controlled by fluid and/or electrical systems.
Such prior automatic transmission drives were subject to numerous disadvantages including their bulk or size, weight and the complicated nature of required shifting and control systems. Furthermore, prior transmission drives required continuous maintenance and the replacement or repair of various wear prone components such as bands, seals, torque converters and the like. Attempts at providing stepless transmission drives with or without fluid couplings proved commercially unfeasible. The products of such attempts suffered from the inability to generate an acceptable range of torque ratios, the inability to attain a vehicle brake condition without engine stall or without the use of a fluid coupling and the inability to attain a one to one or overdrive ratio at vehicle cruising speed. Further, the range of available ratios necessary to generate adequate torque for efficient operation under variant torque loads, e.g. from a vehicle stopped position to cruising speed, was not possible.